In the fields of brain surgery, cardiac surgery, and the like, an operation microscope is used to observe an affected part and conduct an operation in an enlarged field of view. The operation microscope used for such surgery has a plurality of functions such as focus adjustment and zoom adjustment. An operator keeps his or her eyes in contact with eyepieces of the operation microscope and uses both of his or her hands for the operation. Accordingly, the functions of the microscope are generally changed from one to another with a footswitch placed on the floor. The footswitch is provided with a plurality of control switches that are manipulated by the sole of a foot of the operator to change the functions from one to another.